SJ23 Tech Tip F38, (2023-03-01) Bob Schimmel, Greg Overton.


Mainsail Cover - Conventional and Stack Pack.

CONVENTIONAL COVER - A mainsail cover of Sunbrella prevents UV damage to the sail when it isn't used.  It also prevents birds from pooping on the sail!  Many sailors customize their cover with the name of the boat.  I much prefer to cover the mainsail than remove it from the boom after each float.  As the expression goes: "It's definitely the lesser of two evils." 
  • The fabric must be water proof and able to breathe so the sail can dry.  Use Sunbrella or equivalent.
  • The bottom should be open between the SS snaps to let the sail breathe.  Having said this, it is not unusual to be sprinkled with rain water when hoisting the mainsail.  I seldom pack the mainsail when wet but sometimes it is unavoidable.
  • The most forward SS snap is located about a foot behind the mast to ensure the wind does not open it.
  • The most aft SS snap is located at the very end of the cover to prevent the fabric from flapping to death.
  • The cover should be able to stand up to a very strong wind.  Although, a few times I've spiralled a line around the cover to secure things.  In hurricane strength wind I suggest removing the boom with mainsail cover on it, then slide the whole works into the cabin.  I've had to do this twice with Panache.  It's the quickest and easiest protection to ride out a vicious storm.

DON THE COVER - I place Panache's rolled up cover over the boom just behind the mast, similar to throwing a saddle on a horse.  The top straps are knotted around the mast just above the raised spinnaker ring.  The internal flap is folded against the front of the mast to protect the anodized finish from the YKK zipper that is done up (bottom to top).  The bottom straps are tied under a cleat to tension the front a bit.  Then the cover is unrolled towards the end of the boom where the end straps are tied around the boom, tensioning the cover a bit to smooth the wrinkles.  Finally the SS snaps along the bottom are done up.

I also set the main sheet to starboard, secured with a line tied to the bottom of the starboard stanchion, pulling against the main sheet to keep the boom from swinging.  The topping lift keeps the boom just above my head.  I board the boat from port. 

DOFF THE COVER - The sail cover is usually rolled up from the aft end and stored on the forward berth while underway. 

The internal protection flap.

Bottom straps under the cleat.

End of boom straps.

A smooth cover can withstand lots of wind.


Dimensions of sail cover laid out flat on the ground.
The heavy duty YKK zipper goes the full frontal length, 46".


2023 - I finally replaced the short strap on the aft end of the cover with a longer reinforcing one to straddle a seam where I extended the cover to full length.  The end of this reinforcing strap includes a SS ring to minimize wear from the tie down straps.  At the date of this writing Panache's cover is about 45 years old.  I've added a few bits and pieces over the years to improve it, and repaired loose stitches, but not much else.  It has also received occasional water proofing with silicon spray but I have never seen the need to wash it, thinking that the rain could do that job.  However, after all the years of service I thought it high time to give it a thorough water proof treatment.  First I washed it in a laundry tub where to my surprise a lot of coal dust came out.  This is from the adjacent open pit coal mines.  Then I applied NIKWAX TX.DIRECT Spray-on till it saturated the fabric.  The advantage of Nikwax over silicon spray is that it can water proof wet weather fabric and retain breathability.  I like the fact that the bottle has a pump, negating the propellant that can affect the chemical cocktail creating the water proofing.  Nikwax can actually water proof down feathers in a sleeping bag so you stay toasty warm in damp weather. 

Panache's cover has survived so many storms that I lost track and shows no sign of failing.  This is the one redeeming quality that keeps me from installing a stack pack.  Look after yours. 

STACK PACK - A stack pack is an improvement on the conventional mainsail cover since all you have to do is pull the zipper along the top to expose the mainsail for hoisting.  This speeds deployment and more important, speeds dousing for inclement weather.  Its all in keeping with the edict that, "If its quick and easy to do you are more likely to cover the sail quickly to protect it".  The covers stay on the side of the boom while sailing so you don't have to pack it away, eliminating another loose item on a berth.

And finally some sailors object to the loose cloth hanging there and have figured out how to pucker the cloth up along the boom, leaving the mainsail fully exposed and things neatly stored.  This clever bit takes some ingenuity.  The better designed stack pack can be pulled tight against the boom so it doesn't flop around when sailing. 

Closing the front was problematic with the early versions as they would catch wind.  Experimenting with different techniques solved this problem with designs that wrap around the mast as shown in the example at right.  Other designs tuck it on the mast.  In many cases the portion that goes around the mast is tucked in one side along the boom.  On some designs it is removed and stored in the cabin.

The lazy jacks typically hold up each side of the stack pack with the assistance of a PVC rod through the hem along the top.  This makes catching the mainsail slick and pulling the zipper along the top easy.  The downward slope to the end of the boom sheds rain, albeit into the cockpit.  But that's what cockpit drains are for.

This one looks like a Sailrite design.


If you look carefully, the front portion that wraps around the mast, is the only part that detaches.  The remainder stays on the boom as part of the lazy Dutchman system.  Its a clever design that makes it quite easy to don and doff for one person.  No more stretching the cover to the end of the boom.  Only one zipper from what I can tell.

I think the label reads AF Sails.



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